Compilare: user.cpp: In function ‘void backtrack(std::vector<int>)’: user.cpp:17:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2; i < v.size(); i++) ^ user.cpp:19:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v.size() - 1; i++) { ^ user.cpp: In function ‘int main()’: user.cpp:33:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("armate.in", "r", stdin); ^ user.cpp:34:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("armate.out", "w", stdout); ^ user.cpp:36:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &N, &Q); ^ user.cpp:40:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^ user.cpp:45:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^